1. Field of the Invention
The present invention relates to a drive tool for fasteners and more particularly to a screwdriver specially adapted to interact with a combo or uni-screw which has two slots that cross at their centers to accommodate either a type flat-blade screwdriver, or a phillips-type blade screwdriver.
2. Prior Art
When turning any screw such as a combo screw, sometimes the situation dictates the use of only one hand, as in the case when the screw is difficult to see and/or access. This often requires that the screwdriver blade be repositioned onto the head of the screw with every partial turn. Having to repeatedly mate the screwdriver blade with the screw can make a tough job even tougher. To add to the frustration, both standard flat-blade and standard phillips-blade screwdrivers have a tendency to slip out from the properly mated turning position during turning.
Accordingly, the present invention was developed to provide a screwdriver blade that enables easier insertion of a screwdriver blade into a combo screw while providing more secure retention of the screw head during torquing.
There are many screwdriver blades in existence. U.S. Pat. No. 4,590,825 to Vaughn discloses a specially designed screwdriver blade that mates with a corresponding screw. The screwdriver blade has an bowtie-shaped arcuately convex blade that interacts with a concave bowtie-shaped slot in the head of the screw. A centrally disposed conical tip formed on the end of the blade mates with a conical recess in the screw. This type of screwdriver can not be used with standard combo screws of the type described above.
U.S. Pat. No. 5,528,966 to Coppejans discloses a screwdriver blade designed to interact with combo screws.
The screwdriver blade disclosed in Coppejans has a phillips-type screwdriver tip that extends beyond the flat-blade tip portion to provide a blunted cross-shaped tip on the end of the combo screwdriver blade.
U.S. Pat. No. 4,105,056 to Arnn, the inventor of the present invention, discloses a flat screwdriver blade having a foot portion, disposed at the screwdriver tip, that is used for reducing the usual slippage associated with flathead screwdrivers. Typically, screwdriver blades have converging flat sides that cause the flathead screwdriver to slip out of proper torquing position, but the foot portion of the blade disclosed in the Arnn '056 patent bites into the screw to prevent this slippage. The disclosure of the Arnn '056 patent is herein incorporated by reference.
Another patent to the inventor of the present invention, U.S. Pat. No. 3,913,647, discloses a phillips-type screwdriver blade having foot portions on each side of the four phillips-type blades. These foot portions interface with the crossed slots of the phillips-type screw to reduce the likelihood of slippage that results during torquing. The phillips-type blade of the Arnn '647 screwdriver is similar to that of a standard phillips-type blade screwdriver in that the tip has a cross shape. The disclosure of the Arnn '647 patent is herein incorporated by reference.